Program: GS-2009B-Q-78

We propose using T-ReCS to determine the time dependence of an unexpected compact hot spot in Neptune's stratosphere which is offset from its seasonally hot south pole. Images of Neptune's stratospheric emission in 2003 and 2005 were consistent with the expectation that the south pole would be warmer than the rest of the planet as a result of decades of continuous solar heating. But in 2006, an unexpected compact hot region was detected in stratospheric emission at a latitude of approximately 70 deg S and rotating with a 12-hour period. Our conjecture that this might be a singular event, such as a cometary impact, was disproven when we re-discovered it in single 2007 N-band T-Recs and 2008 12.5-micron Subaru COMICS acquisition images. Because it is clearly not a rare phenomenon, we propose to image Neptune over a wide longitude range at three wavelengths sampling emission from different stratospheric levels. Our primary goal is to determine whether this hot spot is a time-dependent phenomenon or a more permanent feature of Neptune's stratosphere. This will allow us to discriminate among various potential causes of the phenomenon. We are submitting a similar proposal for Gemini North Michelle time to observe longitudes unavailable to Gemini South.